Premium
Light and electron microscopic studies of the effects of p ‐chloroamphetamine on the monoaminergic innervation of the rat spinal cord
Author(s) -
Ridet JeanLuc,
Geffard Michel,
Privat Alain
Publication year - 1994
Publication title -
journal of comparative neurology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.855
H-Index - 209
eISSN - 1096-9861
pISSN - 0021-9967
DOI - 10.1002/cne.903430208
Subject(s) - monoaminergic , spinal cord , p chloroamphetamine , serotonergic , biology , electron microscope , axon , anatomy , neuroscience , efferent , serotonin , immunocytochemistry , monoamine neurotransmitter , postsynaptic potential , dopaminergic , dopamine , afferent , endocrinology , biochemistry , physics , receptor , optics
A previous report has shown that small diameter serotoninergic (5‐HT) axons innervating the forebrain are selectively eliminated by treatment with an amphetamine derivative, (±) p ‐chloroamphetamine (PCA; Mamounas et al., [1991] J. Comp. Neurol. 314:558—586). It is well known that the spinal cord is the target of numerous monoaminergic fibers of different types. We have previously shown that the dorsal and ventral horns and the intermediolateral cell column are innervated by numerous serotonin‐, noradrenaline‐ and dopamine‐containing axons, including both thin axons with small varicosities and beaded axons with large varicosities. In all these regions, the large majority of fine indolaminergic fibers do not establish synaptic contacts, contrasting with the beaded axons which mostly exhibit synapses. The present work was conducted to study the effect of PCA on the monoaminergic innervation of the adult rat spinal cord. Animals received two subcutaneous doses of PCA 24 hours apart and were perfused 3 weeks later. Immunocytochemistry was performed to detect 5‐HT, noradrenergic and dopaminergic fibers by using light and electron microscopy. Light microscopy revealed that PCA treatment caused a marked and selective elimination of the fine 5‐HT‐immunoreactive fibers, mainly found in the dorsal horn, but spared all other larger axons. This selective effect on the dorsal horn innervating thin 5‐HT fibers was confirmed with the electron microscope by calculating the synaptic incidence(s) of monoaminergic innervation. These results suggest that fine and beaded 5‐HT axons correspond to two anatomically, biochemistry and pharmacologically different types of fibers, which could arise from two subpopulations of brainstem neurons.In addition, this drug could be used to provide an experimental animal, devoid of 5‐HT nonsynaptic fibers, thereby facilitating a study on the role of dorsal horn nonsynaptic system in pain modulation. © 1994 Wiley‐Liss, Inc.